Sensing devices for use in the medical arts are well-known. For example, sensors are frequently used to observe the function of a subject's heart by detecting the sound and electrical impulses it emits. Anyone who has undergone a heart stress test has been fitted with several sensors to observe heart function, respiration, body temperature, and the like during the course of the test. Ten sensors or more are frequently used in such a test. Each sensor is coupled by a hard-wired connection extending from the sensor to a monitoring unit, i.e., at least one wire physically connecting each sensor and the monitoring unit, and each sensor provides a substantially continuous analog signal to the monitoring unit. Within the monitoring unit, the signals from each of the sensors are amplified and conditioned to provide corresponding data signals, which may then be recorded and/or observed during the test.
To securely attach the sensors to the subject each is first bonded or coupled to a suction cup or similar attaching pad. The suction cup provides the attaching force for securing the sensor to the subject in conjunction with an adhesive or tackifying agent. Sensor attachment often also requires the removal of any of the subject's body hair in the locality of the sensor.
Unfortunately, this arrangement for attaching sensors and recording the data from the sensors causes discomfort to the subject and may further lead to data errors. The sensor attachment must be sufficient to not only support the weight of the sensor, but to also support forces introduced by the hard-wired connection. In addition to the added weight of the wire itself, there are dynamic, "tugging," forces resulting from the wires extending from the subject to the monitoring unit. The attachment is therefore made larger and more aggressive to securely attach the sensor to the subject sufficiently to sustain these additional forces. This causes discomfort to the subject in both attaching the sensors, i.e., if additional shaving or skin preparation is required, and removing the sensors.
Stringing numerous wires from the subject to the monitoring unit presents its own set of problems. The wires themselves restrict the subject's movements. During a stress test the subject is required to walk or jog on a treadmill and needs to move freely. Other subjects, such as a recovering cardiac patient, may be reclined in bed and the wires may inhibit their ability to freely and comfortably sleep restricted. The wires further lead to data errors as they are frequently the cause of the sensors becoming detached due to the added weight and tugging forces. Furthermore, data can not be collected and reported unless the subject is coupled to a monitoring unit and therefore within its close proximity.
Use of suction cups and similar attaching structures also increase the required maintenance of the sensors and the monitoring system. After each use, the suction cups must be thoroughly cleaned and sanitized before the next use. The wiring connections require periodic inspection and repair, and they may add to the setup time to ensure none of the wires interferes with the subject's movements.
Thus a need exists for a sensor that eliminates the need for aggressive attachment and which is capable of reliably reporting data therefrom.